Well, that's a crank rebuild and a rebore for starters.
Ne'mind, it's only money.
Who are you by the way?
Do you know anything about bikes?
Which bit of the world do you inhabit?
Anyway, I've lots of 550 spares when you realise you need some!!!
South Yorkshire's the name, 550s' the game......
I suspect the oil pump is knackered - unless there's no oil in the tank of course.
Our Baz on here rebuilds these for a living, at reasonable prices too!! memberlist.php?mode=viewprofile&u=2
Just done me 2 x 550 engines.
Yours appears to be either an early iron bore UK model or a US import, so barrels are a bit cheaper anyway.